RESUMO
The development of melanoma and its precursor lesions has been associated with intense intermittent sun exposure and the deleterious effects of ultraviolet (UV) light (1). This is supported by epidemiologic data as well as several animal models in which melanoma could be induced or promoted by UV irradiation (Table 1). It remains to be elucidated what changes UV light induces in the human pigment cells at the molecular level that trigger malignant transformation. Experimental animal models established to date have helped us to understand the etiology and pathobiology of melanoma, but they do not necessarily mirror the biology of human melanoma development. The skin morphology in animals differs substantially from that in humans, and melanocytes show a different distribution pattern. In mice, melanocytes are mainly located in the hair follicles, whereas in humans, melanocytes are found epidermally at the basement membrane zone. The number of cell layers of the epidermis is, for the most part, markedly less in mice than in humans (Fig. 1).
RESUMO
An important approach in studies of normal, diseased, and malignant cells is their growth in culture. The isolation and subsequent culture of human eplderma1 melanocytes has been attempted since 1957 (1-5), but only since 1982 have pure normal human melanocyte cultures been reproducibly established to yield cells in sufficient quantity for biological, biochemical, and molecular analyses (6). Selective growth of melanocytes, which comprise only 3-7% of epldermal cells in normal human skin, was achieved by suppressing the growth of keratinocytes and fibroblasts in epidermal cell suspensions with the tumor promoter 12-O-tetradecanoyl phorbol-13-acetate (TPA) and the intracellular cyclic adenosine 3', 5' monophosphate (cAMP) enhancer cholera toxin, respectively, which both also act as melanocyte growth promoters. Recent progress in basic cell-culture technology, along with an improved understanding of culture requirements, has led to an effective and standardized isolation method, and special culture media for selective growth and long-term maintenance of human melanocytes. The detailed description of this method is aimed at encouraging its use in basic and applied biological research.
RESUMO
The poor prognosis of gallbladder cancer and the presence of high-risk populations make the identification of a screening test for this disease very desirable. As part of an ongoing case-control study of gallbladder cancer being conducted in Mexico City, Mexico, and in La Paz, Bolivia, blood specimens were sought from all patients with cancer of the gallbladder and on controls of similar age and sex undergoing upper abdominal surgery. Each sample was analyzed for carcino-embryonic antigen (CEA) and CA 19-9. Using the specimens from Bolivia, a serum CEA cutoff of 4.0 ng/ml yielded a sensitivity of 50.0% and a specificity of 92.7%, while a serum CA 19-9 cutoff of 20.0 units/ml yielded a sensitivity of 79.4% and a specificity of 79.2%. Using ROC curve analysis, the latter was a much better test than the former (p less than 0.05). Using the tests in series or in parallel did not substantively improve the results. The specimens from Mexico were used for validation purposes, and yielded very similar results. In conclusion, serum CA 19-9 and CEA are fairly good tests for discriminating patients with gallbladder cancer from patients with gallstones and no cancer, the former being a better test than the latter. These tests may be useful in identifying disease recurrences. In addition, if a sufficiently high-risk population could be identified, this could potentially become a useful screening test for this serious disease, allowing early intervention. However, additional data are needed prior to recommending this clinically.